This invention relates to the fields of digital filters and binary threshold detection, and more particularly to a programmable filter used to discriminate between actual transitions in the output of a comparator or threshold detector and false transitions, due to noise or other spurious inputs, that are characterized by their short duration.
When a comparator or threshold detector is used to determine when a signal makes a transition across a voltage threshold, noise can cause short-term transitions which do not reflect the intended operation of the circuitry. This problem is particularly acute where the threshold voltage and the quiescent level of the signal are always close together or where the signal voltage is changing slowly through the threshold voltage so that the two levels are close together for a significant period of time.
What is desired is a way to discriminate between relatively long term transitions in the output of a comparator that are intended by the designer to indicate an actual transition and shorter term transitions that are the result of noise or other spurious events.